1. Field of the Invention
The present invention relates to an inference system having a frame structure and storing method of inheritance information therein.
2. Description of the Related Art
Generally, a dynamic knowledge such as data in an inference system is represented in a hierarchical frame structure with an inherent effect. In such a hierarchical frame structure with inherent effect, information which is stored in a parent frame is inherited from the parent frame by a child frame. When information which is stored in the parent frame is updated, the information inherited from the parent frame by the child frame is also updated. However, the information inherited by the child frame cannot be updated by the child frame.
FIG. 8 is a schematic describing such a hierarchical frame structure with inherent effect.
In the figure, reference numeral 11 is a parent frame; reference numeral 12 is a child frame of the parent frame 11; and reference numeral 13 is a child frame of the child frame 12. The parent frame 11 has information a intrinsic thereto. The child frame 12 has information b intrinsic thereto along with the information a inherited from the parent frame 11. Although the child frame 13 has information a and b inherited from the child frame 12, it does not have intrinsic information. In other words, since the parent frame 11 has the intrinsic information a, the information a is inherited by the child frame 12. In addition, since the child frame 12 has both the intrinsic information b and the information a which is inherited from the parent frame 11, the information a and b are inherited by the child frame 13. When the information b of the child frame 12 is updated to information c, the child frame 12 has the information a and c. Thus, the information a and c are inherited by the child frame 13. In other words, when the information which is stored in the child frame 12 is updated, the information which is stored in the child frame 13 is also updated. However, the information a which is stored in the child frame 12 cannot be updated to information d because the information a is information which is inherited from the parent frame 11. In this case, an update operation from the information a to the information d should be conducted in the parent frame 11. In other words, when the information a is updated to the information d in the parent frame 11, the information d is inherited by the child frame 12. In this case, the child frame 12 has the information d and b. On the other hand, the child frame 13 has the information d and b.
There are two methods for storing inheritance information in such an inference system with knowledge in frame structure. In one method, both information which is intrinsic to a frame and information which is inherited by the frame are stored therein (see FIG. 9 (a)). In the other method, only information which is intrinsic to a frame is stored therein (see FIG. 9 (b)).
In the method shown in FIG. 9 (a), when information which is stored in a frame is updated, information to be inherited by the frame cannot be updated. In the following, the case where information which is intrinsic to a frame is updated will be described. When information Which is intrinsic to a frame is updated, if the frame has child frames, the information to be inherited by the child frames is updated hierarchically frame by frame. For example, when the information a stored in the parent frame 11 is updated to the information d, the information which is stored in the child frame 12 becomes d and b and the information which is stored in the child frame 13 also becomes d and b. In such a method, when information which is stored in a frame is referenced, the following operation takes place. In the case where information which is intrinsic to a frame is referenced, when the frame is accessed, the information a which is intrinsic to the frame can be referenced. For example, as shown in FIG. 9 (a), when the parent frame 11 is accessed, the information a which is intrinsic to the frame can be referenced. On the other hand, in the case where information to be inherited by a frame, when the frame is accessed, the information to be inherited by the frame is referenced. For example, in FIG. 9 (a), when the child frame 13 is accessed, the information a and b which have been inherited by the frame can be referenced.
In the method shown in FIG. 9 (b), when information which is stored in a frame is updated, only the information which is intrinsic to the frame is updated. Since information to be inherited by a child frame has not been stored therein, it is not necessary to access the child frame. Moreover, in such a method, when information which is stored in a frame is referenced, the following operation takes place. In the case where information which is intrinsic to a frame is referenced, when the frame is accessed, information which is intrinsic to the frame can be referenced. For example, in the case as shown in FIG. 9 (b), when the parent frame 11 is accessed, the information a which is intrinsic to the frame can be referenced. On the other hand, when information to be inherited by a frame is referenced, an ancestry with intrinsic information which is inherited by the frame is searched and thereby the information is referenced. For example, in the case as shown in FIG. 9 (b) where the information which is stored in the child frame 13 is referenced, since the child frame 13 does not have information which is intrinsic thereto and does not store information to be inherited thereby, the intrinsic information b stored in the child frame 12 and the intrinsic information a stored in the parent frame 11 are hierarchically searched and referenced.
As was described above, information stored in the aforementioned inference system is updated and referenced in different manners depending on the storing methods.
On the other hand, knowledge in the inference system is handled in different manners depending on whether it is inferred or not. The state when inference system inferred is named inference state, while the state where knowledge is not inferred is named out-of-inference state or knowledge editing mode. In other words, in the out-of-inference state, the user of the system mostly edits the knowledge. In other words, the knowledge is mostly updated. On the other hand, in the inference state, since the edited knowledge is used, it is mostly referenced.
Then, for the cases where information stored in a frame is updated and referenced, the storing method of knowledge shown in FIG. 9 (a) and that shown in FIG. 9 (b) will be compared in the following.
First, in the case where information stored in a frame, these methods are compared.
In the storing method shown in FIG. 9 (a), information to be inherited by a descendant frame (which is a frame a plurality of generations down from another frame) is updated through the generations. On the other hand, in the storing method as shown in FIG. 9 (b), only information stored in a frame as intrinsic information is updated. In other words, in the case where information stored in a frame is updated in the storing method shown in FIG. 9 (a), when the frame has child frames, information which is intrinsic thereto should be also updated. Thus, the efficiency of that method is worse than that shown in FIG. 9 (b). In particular, in the out-of-inference state, it is mostly updated. Thus, the storing method shown in FIG. 9 (a) has a problem.
Then, the case where information stored in a frame is referenced will be described.
In the storing method of knowledge shown in FIG. 9 (a), even if information to be referenced is information to be inherited and is intrinsic to the frame, the frame is accessed. On the other hand, in the storing method of knowledge shown in FIG. 9 (b), when all information of a frame is intrinsic thereto, it is possible to access only the frame. However, if the information includes information to be inherited, it is necessary to reference the information hierarchically through the ancestry frames. In other words, in the case where information stored in a frame is referenced, when the frame has information being inherited, the storing method shown in FIG. 9 (b) is worse than that shown in FIG. 9 (a). In particular, in the inference state, since knowledge is mostly referenced, it is said that the storing method shown in FIG. 9 (b) has a problem.